1. Field of the Invention
This invention relates to lasers and in particular to coupled waveguide lasers, such as CO.sub.2 coupled waveguide lasers.
2. Description of the Prior Art
Techniques for the design and construction of waveguide lasers, such as those used in applications requiring high power, have been developed to increase the power available from conventional lasers, such as CO.sub.2 lasers. In order to overcome power density limitations in optical components, coupled strip waveguide lasers and slab waveguide lasers have been developed to spread the laser beam power across a greater area to reduce power densities without reducing total laser power.
A conventional coupled waveguide laser operates on a slot coupling principle which uses a series of slots milled in an insulating material, such as aluminum oxide or aluminum oxide coated aluminum, to form a plurality of parallel channels or slots in an insulating waveguide bed. The slotted insulating channel is positioned between a pair of conducting aluminum plates to which the RF energy is applied. The height of the insulating wall is reduced between the slots to create coupling regions in Which phase coupling occurs between the channels. The coupling which occurs in these coupling regions between adjacent slots or channels introduces substantial loss to the in-phase coupled mode in conventional slot coupled designs so that although coherent, such channels are primarily coupled out-of-phase resulting in an undesirable, twin peak far field power distribution.
An alternate to the slot coupled waveguide laser is the single slab channel laser in which a large width to height ratio is used with a single slab to reduce power density requirements for components. However, high order Gaussian modes tend to dominate the oscillation in single slab lasers so that an unstable resonator has to be used to suppress the high order modes and make the fundamental mode dominant. The use of such unstable resonators increases the complexity of such devices.
What is needed are techniques for permitting higher power, lower power-density operation of waveguide lasers without the limitations, such as out-of-phase coupling or the need for unstable resonators, of the conventional designs.